1. Field of the Invention
The present invention relates to an apparatus for gathering earthen cores extracted from vertical holes and a roller which drives the main conveyor belt of the core-gathering apparatus.
2. Prior Art
Japanese Patent Application Kokai (Laid-Open) No. 63-248305 discloses an example of a core-gathering machine. This machine digs the ground with cylindrical tines and extracts earthen cores (called "cores" hereinafter). Then, it conveys and collects the cores while holding the cores between a main conveyor belt which in a reversed Z (" ") shape (when viewed from one side) and an auxiliary conveyor belt which is in an I-shape (when viewed from the side).
However, the conventional machine is not completely satisfactory from the standpoint of receiving and conveying cores from the core-gathering apparatus. In particular, though the main conveyor belt in the core-gathering machine is driven by a main conveyor belt drive roller (called "drive roller"), during the operation the position of the main conveyor belt shifts in the axial direction of the drive roller as a result of differences in the load resistance, etc. This results in mis-positioning of the belt. When the main conveyor belt is thus mis-positioned, a desirable conveying of the cores is naturally hindered.
Moreover, the main conveyor belt rubs against the side plates, etc. which are installed on both sides of the belt. This results in that the belt and side plates are easily damaged.
The above problem is derived from the following functional characteristics of the main conveyor belt: i.e., the main conveyor belt is a sheet-form belt, having a considerable width. In addition, the distribution of cores carried by this belt is not uniform in the direction of width.
In particular, if the distribution of the cores is biased in the direction of width, the load resistance can vary. As a result, the main conveyor belt tends to lag on the side where the load resistance is larger. Thus, the belt is shifted in this direction. Even if the tension of the main conveyor belt is increased overall or adjusted in the direction of the width in an attempt to prevent the shifting thereof, the effect is not satisfactory. In short, if the main conveyor belt shifts in its position, a means forcibly returning the belt to its original position is required. This might conceivably be accomplished by forming the center of the drive roller higher than the edges thereof. In this case, however, how high the center should be is another problem. If the center of the belt is too low, the inhibiting force which prevents positional shifting of the belt will be small. On the other hand, if the center of the belt is too large, the main conveyor belt may not come into contact with the drive roller at the ends of the roller since the main conveyor belt has a large width. In such cases, a sufficient driving force cannot be obtained.